This invention relates to electromagnetic projectile launching systems and more particularly to such systems which utilize an exploding fuse in an air tight cartridge to generate a plasma with sufficient pressure to impart starting momentum to a projectile.
Electromagnetic projectile launchers are known which comprise a pair of conductive rails, a sliding conductive armature between the rails, a source of high current and a switch for commutating this current into the rails and through the armature. Current flow through the rails and armature results in an electromagnetic force on the armature which propels it along the conductive rails. Launchers which utilize a sliding metallic armature have experienced considerable rail damage caused by the sliding armature, particularly where high armature velocities are involved. In these cases, a plasma (arc) armature may be more suitable.
The principal disadvantage to the use of a plasma propelling armature has been the damage that occurs to the breech section of the launcher rails during formation of the plasma. Once the plasma is moving, very little, if any, damage occurs to the rails. Copending commonly assigned application entitled Electromagnetic Launcher With Self Augmented Rails, Ser. No. 137,059, filed Apr. 3, 1980 by Kemeny and Litz, now U.S. Pat. No. 4,347,463, issued Aug. 31, 1982 discloses a means for establishing an arc for propelling a projectile comprising a shooting wire or fuse which initiates current flow between the rails, disintegrates, and thereby forms an ionized plasma or arc through which current continues to flow. Because the mass ratio between a projectile and a plasma armature is greater than that between a projectile and a sliding metallic armature, more efficient utilization of available launch package energy is possible with plasma drive. In addition, plasma drive provides a means for launching ultra high velocity projectiles with good shot-to-shot reproducibility. Therefore, the application of plasma driven projectiles in multi-shot systems is appropriate. Such systems include rapid fire air defense systems and impact fusion reactors.
Several methods have been suggested for initiating an arc or plasma in electromagnetic launcher systems. These procedures are primarily directed toward resolving the problem of creating the plasma armature and minimizing the resulting thermal damage of the launcher rails. Ablation of the rail surfaces is caused by a slow moving or stationary arc and occurs during initial acceleration of the projectile from zero velocity. At higher projectile velocities, the effects of this thermal phenomenon become increasingly insignificant. Therefore a means for imparting initial momentum to the launch package is desired to prolong launcher rail life.
Excessive launcher rail damage has been observed where a copper fuse is blown to form a plasma composed mainly of copper ions. This resulted in sputtered metal from a partially vaporized fuse and thermal erosion of the rail surfaces from a slow moving or stationary arc over only a short length of rail starting at the original location of the fuse in the breech. The present invention seeks to minimize launcher rail damage caused by slow moving plasmas in the breech area by utilizing an exploding fuse in an air tight insulating cartridge to generate a plasma with sufficient pressure to impart starting momentum to the projectile before electromagnetic forces dominate to propel the projectile along the launcher rails.